1. Field of the Invention
The present invention generally relates to a throttle valve actuator used for controlling engine power of an automobile. More specifically, the present invention is directed to a throttle valve actuator mutually controlled by an accelerator pedal and also an electric motor.
2. Description of the Related Art
Various attempts have been made in a throttle valve actuator to control a throttle valve of an automobile. One of the conventional throttle valve actuators is disclosed in Japanese KOKAI (Disclosure) patent application No. 61-215436 (1986) filed by Mitsubishi Denki K.K. in Japan.
FIG. 1 shows a schematic diagram of the above-described conventional throttle valve actuator. Referring to FIG. 1, reference numeral 1 designates differential gears including a pair of opposed gears 2 and 3 and a pair of opposed gears 5 and 6 meshed with the gears 2 and 3. The gears 2 and 3 are rotatably supported to a shaft 4. A motor 7 is provided to rotate the gear 2 of the differential gears 1 through a gear 8. An accelerator pedal 9 is provided to rotate the gear 3 of the differential gears 1 through an accelerator wire 10, a pulley 11 and a gear 12 by depression force to be applied to the accelerator pedal 9. A gear 13 is mounted on a shaft 14 supporting the gears 5 and 6, and is meshed with a gear 15. A throttle valve 16 is operated through the gear 15 by the rotation of the gear 13.
When the accelerator pedal 9 is depressed, the accelerator wire 10 is drawn to rotate the pulley 11 and the gear 12 and thereby rotate the gear 3. At this time, when the motor 7 is in an inoperative condition, the gear 3 is rotated to rotate the gear 13 and the gear 15 and, thereby open and close the throttle valve 16. When the motor 7 and the accelerator pedal 9 are simultaneously operated, both driving forces thereof are outputted, or transported to the gear 13. Accordingly, the driving force of the gear 13 is the sum or difference between both the driving force of the motor 7 and of the accelerator pedal 9.
However, as the driving force of the motor 7 and the accelerator pedal 9 are applied in parallel to the same gear 13, a reaction of the torque of the motor 7 is transmitted to the accelerator pedal 9. As a result, when a car driver's foot is put on the accelerator pedal 9, a change in the depression force applied to the accelerator pedal 9 is felt through his foot on the pedal 9 by the driver because of the rotation of the motor 7, resulting in deterioration of the drive feeling, i.e., drivability.
Further, in the event that the motor 7 fails to operate, the throttle valve 16 cannot be returned from a controlled position upon occurrence of such motor malfunction to a valve closing position. Thus, the conventional actuator has a problem in fail-safe structure.
Additionally, when the accelerator pedal 9 is rapidly depressed under the condition where the throttle valve 16 is opened at a certain angle by the motor 7, there is a possibility of the throttle valve 16 biting a body 17. If a stopper is provided to prevent such body biting, a depression stroke of the accelerator pedal 9 is shortened to cause deterioration of the acceleration feeling.
The present invention has been achieved to solve the above-described conventional problems.
A primary object of the present invention is therefore to provide a throttle valve actuator which may eliminate the interference between the driving force of the motor and the depression force of the accelerator pedal.
It is a second object of the present invention to provide a throttle valve actuator which may ensure fail-safe construction against motor malfunction by quickly interrupting the valve driving by the motor.
It is a third object of the present invention to provide a throttle valve actuator which may prevent the throttle valve from biting the body even when the accelerator pedal is rapidly depressed under the condition where the throttle valve is opened at a certain angle by the motor.